Method of controlling the steering of rear wheels of a motor vehicle with steerable front and rear wheels

Abstract

A motor vehicle has two steerable righthand and lefthand front wheels and two steerable righthand and lefthand rear wheels, a front wheel steering device for steering the front wheels according to the angle through which a steering wheel is turned, a rear wheel steering device for steering the rear wheels, an actuator for actuating said rear wheel steering device, and a control device for controlling the operation of the actuator to steer the rear wheels in a direction which is selectively the same as or opposite to the direction in which the front wheels are turned. The steering of the rear wheels is controlled by determining the speeds of rotation of the four front and rear wheels with respect to the ground, and controlling the operation of the actuator with the control device so that any difference between the speeds of rotation of the front and rear wheels with respect to the ground will be reduced substantially to zero.

We claim: 
     
       1. A method of controlling the steering of rear wheels of a motor vehicle having two steerable righthand and lefthand front wheels and two steerable righthand and lefthand rear wheels, a front wheel steering device for steering the front wheels according to the angle through which a steering wheel is turned, a rear wheel steering device for steering the rear wheels, an actuator for actuating said rear wheel steering device, and a control device for controlling the operation of the actuator to steer the rear wheels in a direction which is selectively the same as or opposite to the direction in which the front wheels are turned, said method comprising the steps of: determining the speeds of rotation of the four front and rear wheels with respect to the ground; and   controlling the operation of said actuator with said control device so that any difference between the speeds of rotation of the front and rear wheels with respect to the ground will be reduced substantially to zero.   
     
     
       2. A method according to claim 1, wherein the operation of said actuator is controlled by said control device so that the difference between the speeds of rotation of lefthand front and rear wheels with respect to the ground will be reduced substantially to zero. 
     
     
       3. A method according to claim 1, wherein the operation of said actuator is controlled by said control device so that difference between the speeds of rotation of righthand front and rear wheels with respect to the ground will be reduced substantially to zero. 
     
     
       4. A method according to claim 1, wherein the operation of said actuator is controlled by said control device so that the sum of the difference between the speeds of rotation of lefthand front and rear wheels with respect to the ground and the difference between the speeds of rotation of righthand front and rear wheels with respect to the ground will be reduced substantially to zero. 
     
     
       5. A method of controlling the steering of rear wheels of a motor vehicle having two steerable righthand and lefthand front wheels and two steerable righthand and lefthand rear wheels, a front wheel steering device for steering the front wheels according to the angle through which a steering wheel is turned, a rear wheel steering device for steering the rear wheels, an actuator for actuating said rear wheel steering device, and a control device for controlling the operation of the actuator to steer the rear wheels in a direction which is selectively the same as or opposite to the direction in which the front wheels are turned, said method comprising the steps of: determining the speeds of rotation of the four front and rear wheels with respect to the ground; and   controlling the operation of said actuator with said control device so that any difference between the sum of the speeds of rotation of the righthand and lefthand front wheels with respect to the ground and the sum of the speeds of rotation of the righthand and lefthand rear wheels with respect to the ground will be reduced substantially to zero.